High durability of dental composite materials is sometimes desired to ensure appropriate performance. In case of high strength dental filling materials high brittleness can cause failures like e.g. cracks within the restauration so that a repair or a replacement might be necessary. In case of temporary materials, especially temporary crown and bridge materials, brittleness may lead to fracture of the material so that the material has to be replaced.
Typical physical parameters for determining brittleness of a material are E-modulus, elongation at break, and impact strength.
Various attempts were undertaken to address this issue.
WO 01/44338 relates to dental composites based on (meth)acrylates comprising certain urethane pre-polymers to reduce brittleness indicated by improved impact strength of the cured composition.
WO 2009/006282 relates to dental composites based on polyfunctional (meth)acrylates comprising urethane, urea or amide groups to reduce brittleness indicated by improved Impact Strength of the cured composition.
U.S. Pat. No. 7,534,909 (Otsjui et al.) relates to a (meth)acrylic ester compound having a specific formula. It is stated that the compound can be used in dental materials and optical parts.
JP 63 248811 (Mitshubishi) describes compositions with high refractive index useful for optical lenses, wherein the polymerizable components used contain halogenated aryl moieties.
However, there is still room for improvement especially with regard to the requirements to be fulfilled with respect to modern dental materials.
Thus, there is still a need for an improved dental composition, which can be used inter alia as a filling material or temporary or long term crown and bridge material.